Binders are useful in fabricating materials from non-assembled or loosely-assembled matter. For example, binders enable two or more surfaces to become united. Binders may be broadly classified into two main groups: organic and inorganic, with the organic materials being subdivided into those of animal, vegetable, and synthetic origin. Another way of classifying binders is based upon the chemical nature of these compounds: (1) protein or protein derivatives; (2) starch, cellulose, or gums and their derivatives; (3) thermoplastic synthetic resins; (4) thermosetting synthetic resins; (5) natural resins and bitumens; (6) natural and synthetic rubbers; and (7) inorganic binders. Binders also may be classified according to the purpose for which they are used: (1) bonding rigid surfaces, such as rigid plastics, and metals; and (2) bonding flexible surfaces, such as flexible plastics, and thin metallic sheets.
Thermoplastic binders comprise a variety of polymerized materials such as polyvinyl acetate, polyvinyl butyral, polyvinyl alcohol, and other polyvinyl resins; polystyrene resins; acrylic and methacrylic acid ester resins; cyanoacrylates; and various other synthetic resins such as polyisobutylene polyamides, courmarone-idene products, and silicones. Such thermoplastic binders may have permanent solubility and fusibility so that they creep under stress and soften when heated. They are used for manufacturing various products, for example, tapes.
Thermosetting binders comprise a variety of phenol-aldehyde, urea-aldehyde, melamine-aldehyde, and other condensation-polymerization materials like the furane and polyurethane resins. Thermosetting binders may be characterized by being transformed into insoluble and infusible materials by means of either heat or catalytic action. Binder compositions containing phenol-, resorcinol-, urea-, melamine-formaldehyde, phenol-furfuraldehyde, and the like are used for the bonding of textiles, plastics, rubbers, and many other materials.
As indicated above, binders are useful in fabricating materials from non-assembled or loosely-assembled matter. Accordingly, compositions capable of functioning as a binder are desirable.